In my earlier invention described and claimed in U.S. Pat. No. 4,499,526 there is disclosed a molded glass reflector member for a lamp unit employing a tungston halogen lamp as the light source which includes a recessed opening at its base end and which further provides an engagement surface for mounting said lamp unit in a conventional socket member. Said lamp unit has already gained popular acceptance for both horizontal and vertical mounting as a precise illumination source in such product applications as photographic projection, lighting displays, and even overhead room illumination. One conventional socket member being used for horizontal mounting of said lamp unit in a photographic projector, so that illumination therefrom proceeds in a horizontal direction, physically supports the lamp unit at the base end by a pair of lamp inlead wires while providing a metal flange at the opposite lamp end which holds the entire lamp unit in place. Vertical mounting of said lamp unit so that illumination projects therefrom in a vertically downward direction such is used in display lighting applications and overhead room illumination requires a still more reliable mounting means to avert accidental dislodgement of the lamp unit from the socket member when subjected to vibration forces and the like. It would be desirable to provide said more reliable mounting means for the lamp unit in the reflector member itself to avert increased costs attendent to fixture modification and especially if such improvement can be incorporated when the glass reflector member is initially molded. Accordingly, the present improvement constitutes a still further modification of the lamp unit disclosed in the aforementioned issued patent which is incorporated herein by reference.
An already known modification of this type lamp unit to improve its retention in the socket member utilizes a single horizontal slot formed in the elongated cavity protruding from the rear side of the reflector member and is formed therein by a sawing or grinding step after the reflector member has been molded. Such modification requires a labor intensive secondary operation and produces stress induced cracks in the glass part which are prone to propogate further enhancing glass failure. Since physical engagement of said glass slot with a mating protuberance located in the socket member will also occur only on one side of this lamp unit, there can also be tilting of the lamp unit in the socket member for improper aiming of the illumination produced therefrom. Additionally, glass chips from this slot can build up in the lamp socket after repeated lamp replacements and lead to premature socket failure with attendent higher operating costs.